X-ray diffraction method

ABSTRACT

An open beam x-ray diffraction system and method are provided including modular x-ray heads for being detachably connected to a base unit having a common drive assembly that shifts the heads in an arcuate path during an x-ray diffraction measurement operation. The heads can be tailored to different performance criteria depending on the needs of the measurement operation that is to take place. To this end, one of the heads can be a microhead that is adapted to take measurements from otherwise difficult to access surfaces, such as on the inside of tubular parts. Enhancements to the drive assembly for improved accuracy and speed are also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of prior U.S. application Ser. No. 11/195,298,filed Aug. 2, 2005, which is a continuation of prior U.S. applicationSer. No. 10/390,479, filed Mar. 17, 2003, now U.S. Pat. No. 6,925,146,issued Aug. 2, 2005, which are hereby incorporated herein by referencein their entirety.

FIELD OF THE INVENTION

The invention relates to a system and method for measuring thestrength-related characteristics of a part material using x-raydiffraction techniques and, more particularly, to a system and methodthat employ such techniques with parts of various sizes andconfigurations.

BACKGROUND OF THE INVENTION

The use of x-ray diffraction techniques for measuring residual stressesin crystalline substances such as metal or ceramic materials iswell-known. The general idea with the use of x-ray diffraction is tosubject the material to the radiation of x-rays with the resultingsensed x-ray diffraction peak interpreted to arrive at a measurement ofa strength related characteristic, i.e. stress, retained austenite,hardness of the part material, to show, for instance, the level fofatigue in the material.

More particularly, the present invention relates to open beam type x-raydiffraction equipment that utilizes a cantilevered x-ray goniometer headhaving fiberoptic detectors carried toward the forward end of the head.In contrast, there are x-ray diffraction systems that are of a closedloop variety in the sense that the x-ray head is positioned at onelocation along a circular mount with the detectors spaced generallyacross from or diametrically opposite to the x-ray head along the circlemount with the part inserted in the space therebetween. In thesesystems, part size is limited due to this orientation of the x-ray headand detectors, and generally, coupons have to be taken from the partthat is desired to be measured. With the open beam approach, coupons donot have to be cut out from parts since the x-ray head and detectors areintegrated with each other. However, current open beam x-ray equipmentstill suffers from shortcoming as described below.

One such problem is that there is no open beam type x-ray apparatus thatcan perform these types of measurements on a wide variety of differentparts and/or different materials or materials with differentcharacteristics such as with respect to crystalline structure.Generally, the size of the goniometer or x-ray tube head relates to thepower required for its operation. With greater power levels, thediameter of the x-ray tube is larger for heat dissipation purposes. Thepower for a goniometer head is selected to generate sufficient x-rayflux for the x-ray diffraction process to take place with particularmaterials or material characteristic.

The problem with the use of larger diameter x-ray heads for takingmeasurement is that with certain parts such as pipes and the like, itwould be desirable for measurements to be taken of the material in theinterior of the part. Depending upon the relative size of the innerdiameter of the pipe and of the head on the x-ray diffraction apparatus,it may be physically impossible for the x-ray head to fit inside thepipe and take a suitable measurement. Also, where part surfaces are inconfined areas such as in close confronting relation to each other ascan be found on fillets of aircraft rotor disks at the roots of therotor blades, set-up of the x-ray diffraction equipment to preciselydirect the x-rays at the surface location from which a measurement isdesired can be difficult, and is usually unwieldy where the large x-rayhead itself has to be manipulated. Since current open-beam x-raydiffraction units have x-ray heads that are specifically tailored to amaterial or materials from which measurements are to be taken, manydifferent sizes and types of x-ray diffraction units generally arenecessary to take measurements on a wide range of different parts thatare of different or materials or material characteristics, and/or havingdifferent configurations raising equipment costs accordingly. Thus,there is a need for an x-ray diffraction system and method that allowfor greater flexibility in terms of the different types of parts andpart geometries from which accurate x-ray diffraction measurements canbe taken.

Another problem in using this equipment is the measurement precisionthat is desirable, and the issues this creates with the system's drivemechanism for pivoting or rotating the tube during a measurementoperation. During x-ray measurement operations, the tube is typicallypivoted to vary the position of the x-ray emitter or collimator fromwhich x-rays are emitted toward the part to obtain more precisemeasurements by way of sampling techniques as opposed to keeping thetube and its collimator fixed relative to the part. As mentioned, thetube is generally cantilevered and is pivoted back and forth along afixed arcuate rack by a motor drive including a pinion gear which pivotswith the tube. In another configuration, the motor pivots the rack whichis fixed to the tube. In both instances, the motor is also part of thecantilevered structure of the current x-ray diffraction units. Thus,current x-ray diffraction units have heavy cantilevered weights,particularly those having larger x-ray tubes. Since the x-raydiffraction techniques employed rely on distinguishing minutedifferences in the diffraction peaks and patterns of the detectedx-rays, precision is required for pivoting the x-ray head. Inaccuraciescan be created in present drive mechanisms with transmission belts thatstretch and/or with backlash problems that occur between meshed gearsdue to play therebetween such as with the above-described rack andpinion arrangement. Therefore, there exists a need for a drive mechanismthat provides for precision movements of the x-ray head for takingefficient and accurate measurements therewith.

Various part sizes and configurations pose yet another problem forstandard x-ray diffraction measurement techniques in that the preferredmeasurement technique, d v. Sine² ψ, cannot be used to measure all partconfigurations. When using this technique, the sensors are positionedsuch that they remain in a plane that is parallel to the plane ofangular rotation of the head itself. This technique is the most accurateway to measure strength related characteristics of parts because of thegeometrical relationship between the x-ray emitter, part, and sensors.However, this technique requires enough room to allow the head tooscillate back and forth without having the sensors hit the part itself.Therefore, there are situations where a different method of measuring,called d v. Sine² χ, must be used. When using this technique, thesensors are in a position that is shifted by ninety degrees about thelongitudinal axis of the emitter from the d v. Sine² ψ configuration sothat the sensors are generally aligned or parallel to the longitudinalaxis of the x-ray tube. Then the head rotates as it normally does duringx-ray diffraction measurements. This sensor configuration allows theuser to take measurements in narrow places such as between the roots ofblades. However, utilizing the d v. Sine² χ technique requires asacrifice in measurement accuracy. Currently, one has to switch x-raydiffraction apparati in order to change from one technique to another.Accordingly, an x-ray diffraction apparatus that has flexibility interms of the measurement techniques it employs would be desirable.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, an x-raydiffraction apparatus is provided having x-ray or goniometer heads thatare modular to allow them to be switched with one another to optimizethe performance of the apparatus. In this manner, measurements can betaken from a wider spectrum of part sizes and configurations and ofdifferent part materials or material characteristics without requiringdifferent x-ray diffraction unit by using the same base x-raydiffraction apparatus in conjunction with different modular heads thatare selected according to the operating requirements for the part fromwhich measurements are to be taken. For instance, if the part includesmeasurement sites that are difficult or impossible to access withstandard larger size x-ray tubes such as pipe interior surfaces, asmaller x-ray head can be exchanged with a larger head and removablyattached to the apparatus for taking x-ray diffraction measurementstherewith. If a high power x-ray head is preferable due to partmaterials and/or geometry, then a larger x-ray head can be exchangedonto the apparatus for the smaller head. As is apparent, rather thanhaving a different x-ray diffraction unit for each different head withthe floor space and expense this entails, the present invention allowsfor a single base unit to be employed with different modular x-ray headsto allow them to be switched with one another to optimize theperformance of the apparatus. Programmable modules can be associatedwith each head to transmit information to the base unit controllerrelating to the size and other operational and performancecharacteristics of the specific head including its x-ray detector systemconnected to the unit for proper operation thereof without the need toenter such information each time a head is exchanged.

The modular heads each have an x-ray tube, and emitter/sensor assembly,and an adapter portion for connecting the head to the base of theapparatus, and more particularly a cooperating adapter portion thereof.The head adapter portion may be a socket that connects to the baseadapter portion in the form of a shaft of the base, the shaft beingdriven by a drive train and motor to shift the x-ray head as describedfurther herein. In the preferred form, the socket is conical, and theshaft has a conical terminus for mating in the x-ray head socket. Topositively fix the shaft in the socket opening, the shaft can include akeyway and the head adaptor may have a key which mates and releasablylocks into the keyway to prevent relative rotation between the shaft andx-ray head detachably connected thereto. Alternatively, the key andkeyway can be reversed with the shaft being keyed and the socketincluding a keyway.

Each x-ray tube head has an emitter or collimator which depends from thetube generally perpendicular to the tube longitudinal axis for directingx-rays down toward the part. An arc mount is provided for detectors ateither end thereof, and the emitter collimator bisects the arc mount, asis the typical configurations for these emitter/sensor assemblies oncurrent x-ray tubes. Accordingly, operation of the motor or the baseunit rotates the output shaft adapter which, in turn, rotates the x-raytube detachably connected to the unit shaft adapter via the socketadapter portion thereof. Thus, rotation of the head adapter portion andthe tube attached thereto causes the collimator carried toward theforward end of the tube to shift along a predetermined arcuate path sothat x-rays are directed at a region on the part from different anglesof attack from the x-ray tube head. Although the x-ray head assembly iscantilevered forward from the base unit, the drive mechanism includingthe motor and drive transmission including the output shaft are alldisposed in the base unit to minimize the cantilevered weight of themodular x-ray heads thus improving the accuracy of the movements thereofin contrast to the heavier prior x-ray heads that had their pivot drivemechanisms integrated at the head to be cantilevered as previouslydescribed.

In another aspect of the invention, an improved drive assembly isprovided which includes an anti-backlash mechanism to provide precisionshifting for the head upon operation of the drive motor. Such precisionshifting enables more accurate x-ray diffraction measurements to betaken. The anti-backlash mechanism preferably employs a split gear thatis associated with the drive train, and more specifically the adaptershaft assembly of the base drive unit. The gear is split axially intogear portions that have their corresponding teeth portions oppositelybiased relative to each other. In this manner, the faces of the teeth ofthe split gear stay firmly engaged against the faces on the teeth of themotor drive shaft gear so as to substantially minimize any loose spacesor play therebetween. Alternatively, the split gear could be provided onthe motor drive shaft for meshing with a gear on the output shaftassembly.

Unlike prior rack and pinion drive systems as previously described, thesplit gear avoids backlash that can occur in the prior drive systemswhen the motor changes direction when the x-ray head has reached the endof its travel along the rack at one end or the other thereof. The rackand pinion system causes inaccuracies to be introduced into themeasurements that are taken by the x-ray head due to the play betweenthe gears as the motor changes directions. In contrast, the presentsplit gear keeps its teeth firmly engaged against the teeth faces of themotor gear even when the motor is changing directions toward the end ofthe arcuate travel path in one direction or the other. Accordingly, thepresent anti-backlash mechanism avoids the inaccuracies caused by theplay between the gear teeth in the prior drive systems.

As previously mentioned, the modularity of the x-ray heads of thepresent x-ray diffraction apparatus enables x-ray heads of varying sizesand/or configurations to be employed on the same base unit. To this end,the heads can include sizes ranging from relatively large heads of, forexample, approximately four inches in diameter, to extremely small ormicro-heads which can be on the order of approximately one and onequarter inches down to three-eighths of an inch in diameter. The windowin the tube aligned with the collimator that allows passage of thex-rays generated in the tube to the collimator is normally brazed to thetube material, e.g. stainless steel. However, the problem with utilizingan intermediate brazing material in the microtube is that it increasesthe chances for melting which increases the potential for contaminatingthe tube and generating leakage from the tube. Accordingly, thepreferred window utilized with the microtube x-ray head is electron-beamwelded to the tube material to avoid intermediate brazing material.

Another adaptation for the microtube is the use of a flexible circuitboard that receives signals from the detectors for processing thereof.The flexible circuit board can conform to the curved surface of themicrotube x-ray head so as to avoid significantly increasing thediameter thereof. Generally, with prior larger x-ray tubes, thedetectors are connected by fiber-optic cabling to a processor unitmounted toward the back of the x-ray head or thereabove thus creatingimpediments for maneuvering the head such as may be required fordifficult part geometries. Accordingly, the use of the flexible circuitboards on the microtube maintains its enhanced flexibility in reachinghard-to-access target surfaces on parts from which x-ray diffractionmeasurements are to be taken.

In the other larger heads in the modular x-ray head set that can beemployed with the present modular x-ray diffraction apparatus, anotheradvantageous feature that can be implemented is the ability to shift theemitter/sensor assembly relative to the x-ray head so that bothprinciple mathematical techniques, d v. Sine² ψ and d v. Sine² χ areavailable to be utilized. While the modularity of the x-ray headsprovided in the preferred system herein allows for the differentemitter/sensor configurations to be fixed on different tubes that can beeasily changed out depending on which measuring technique is to beutilized, the shifting of the emitter/sensor assembly on a particulartube is preferable from a convenience standpoint to avoid having toexchange tubes as has been described.

Typically, the emitter/sensor sub-assembly includes an arc to which thesensors are mounted as previously described. With the sensors in the dv. Sine² ψ orientation, they are offset on either side of the tubelongitudinal axis, and thus can serve as impediments to tubemaneuverability when measuring difficult part geometries. Accordingly,by allowing for the shifting of the sensor arc so that it is in the d v.Sine² χ orientation with the sensors aligned along the tube axis, thex-ray head can be better positioned as the arc is now in a minimallyinvasive orientation thereof, albeit invoking the mathematical techniquethat is less precise for x-ray diffraction purposes.

In one form, a manual actuator is provided which allows an operator tomanually adjust the position of the sensors between the above-describedconfigurations. The manual actuator can be a pin that is biased into aselected one of two apertures corresponding to the configuration for thesensors that is desired. The pin includes a handle pull ring to allow auser to pull it out from the aperture against its bias for shifting ofthe sensors to the other configuration. With the pin aligned with theother aperture, the pull ring is released and the pin is biased into thealigned aperture to fix the sensors in the selected configuration.Accordingly, the pull ring manual actuator allows for very efficient andquick adjustments to be made to the sensor configuration to allow thelarger x-ray heads to be more flexibly employed with a variety ofdifferent part configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an x-ray diffraction system inaccordance with the present invention showing an x-ray head having acollimator and sensors for taking x-ray diffraction measurements from apart fixed therebelow;

FIG. 2 is an exploded perspective view of the x-ray diffraction unitshown in FIG. 1 showing an adaptor between the motor base unit and themodular x-ray head including an output adapter shaft portion of themotor unit;

FIGS. 3-5 are elevational views of different sized modular x-ray headseach including identical rear socket adaptor portions for mating withthe output shaft adaptor portion of the drive unit;

FIG. 6 is a perspective view of the micro-x-ray head of FIG. 5 showing afixed sensor arrangement thereof and a flexible circuit board forprocessing signals from the sensors;

FIG. 7 is a side-elevational view partially in section of the x-ray headof FIG. 6 showing the construction of the tube walls thereof and atarget anode in ghost;

FIG. 8 is a front elevational view taken along line 8-8 of FIG. 7showing front inlet and outlet cooling ports for the tube;

FIG. 9 is a bottom plan view taken along line 9-9 of FIG. 7 showing thewindow formed at the bottom of the tube for directing x-raystherethrough;

FIG. 10 is a plan view taken along line 10-10 of FIG. 1 of the driveassembly showing the motor and the frustoconical configuration of theoutput adaptor shaft end portion;

FIG. 11 is a front elevational view of the drive assembly taken alongline 11-11 of FIG. 10 and showing in phantom the motor drive shaft andan anti-backlash gear assembly associated with the output shaft;

FIG. 12 is a cross-sectional view taken along lines 12-12 of FIG. 10showing a pinion gear on the motor drive shaft meshed with theanti-backlash gear including a biased split gear on the output shaftassembly;

FIG. 13 is an elevational view of the gear assembly of the gear assemblytaken along line 13-13 of FIG. 12 showing the biasing mechanism forurging the split gears angularly opposite to one another;

FIG. 14 is a cross-sectional view of the split gears assembled andbiased relative to each other via springs attached between respectiveposts of each of the split gear members;

FIG. 15 is a front-elevational view of one of the split gear membersshowing slots and posts on one of the faces thereof;

FIG. 16 is a side-elevational view of the split gear member of FIG. 15;

FIG. 17 is a front-elevational view of the other one of the split gearmembers showing posts on the face thereof;

FIG. 18 is a side-elevational view of the split gear member of FIG. 17;

FIG. 19 is a schematic view of the effects of the biasing action onrespective gear teeth of the split gear members showing the gear teethtaking up slack between adjacent gear teeth on the pinion gear;

FIG. 20 is a flow diagram showing the steps for taking x-ray diffractionmeasurements with the present modular x-ray head apparatus;

FIG. 21 is a perspective view of the micro-x-ray head showingalternative water manifolds therefor and having the sensors fixed in thed v. Sine² χ orientation;

FIG. 22 is a side-elevational view of the large tube x-ray headincluding a detector shift assembly and showing the sensors in the d v.Sine² ψ orientation in solid lines and in the d v. Sine² χ orientationin phantom lines;

FIG. 23 is a front elevational view of the head and detector shiftassembly of FIG. 22 showing a manual pull ring actuator for releasablysecuring a rotary shift member to a mount member thereof;

FIG. 24 is a fragmentary bottom plan view of the head and detector shiftassembly of FIGS. 22 and 23;

FIG. 25 is a bottom plan view similar to FIG. 24 showing the detectorsshifted to their d v. Sine² χ orientation aligned with the x-ray tubeaxis;

FIG. 26 is an enlarged side elevational view partially in section astaken along line 26-26 of FIG. 24 showing a spring loaded plunger memberof the pull ring actuator received in aligned openings in the shift andmount members;

FIG. 27 is a bottom plan view partially in section as taken along line27-27 of FIG. 23 showing another opening in the mount member forreceiving the plunger with the detectors shifted to the d v. Sine² χorientation;

FIG. 28 is a side elevation view of another modular x-ray head assemblyfor taking x-ray diffraction measurements from surfaces in small andshallow through openings; and

FIG. 29 is a front elevational view of the x-ray head assembly of FIG.28 showing a lateral adjustment mount for the x-ray detectors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, an x-ray diffraction apparatus 10 inaccordance with the present invention is depicted in a representativeembodiment and set-up with the apparatus 10 including a modular x-raygoniometer head 12 that is detachably connected to base unit 14 fortaking x-ray diffraction measurements from various parts such as theillustrated gear 16 rigidly held by fixturing 17 therebelow. The x-rayhead can be shifted in a plurality of different linear directions suchas in the vertical Z-axis direction as well as in the lateral Y-axisdirection, as shown. X-axis fore and aft direction shifting can also beprovided as well as rotary or pivot shifting of the head 12 aboutdifferent pivot axes. A common drive assembly 18 (FIG. 10-12) shifts thex-ray tube head assembly 12, and particularly the emitter or collimator20 depending from the tube housing 12 a at the forward end portionthereof in arcuate path 22 so that as the tube oscillates back and forthin its arcuate path 22, x-rays are directed at the region on the part 16from a variety of different angles to provide several different datapoints from which measurement information can be gleaned. Frame 19 ofthe base unit 14 can support both the part 16 along with its fixturing17 and the drive assembly 18.

To allow different x-ray generator tube heads or head assemblies (seeFIGS. 3-5 and 28) to be interchanged onto the base unit 14 to be drivenby the common drive assembly 18, an adapter, generally designated 24, isprovided between each of the heads and the base unit 14, as shown inFIG. 2 with respect to head 12. In the preferred and illustrated form,the adapter 24 includes an output shaft end portion 26 associated withthe base unit 18 and a socket portion 28 associated with each of thex-ray heads. Manifestly, the adapter portions 26 and 28 can be reversedon the heads and base unit, although it is preferred to have the shaftportion 26 on the mount 14 so that the set of modular x-ray heads do nothave the small projecting part for its adapter portion 28.

The output shaft adaptor portion 26 and the socket adaptor portion 28may be provided with a conical or frustoconical configuration so thatthey mate together with the conical surfaces in close fitting relationwith each other to provide ease in alignment in making the connectionfor the adapter 24 herein. Rotation of the output shaft adaptor portion26 is generated by operation of the drive assembly 18 for shifting thetube head 12 in its arcuate path 22. For this purpose, a key and keywayconnection can be provided in the adapter 24 as by an axially extendingkey projection 30 formed on the adapter shaft 26 that can fit into anaxial recess 31 formed in the socket 28 when angularly alignedtherewith. In this manner, the output shaft adaptor portion 26 isnon-rotatably received in the socket 28 for transmitting torque from thedrive assembly 18 to the tube head 12 so that it is oscillated in itsarcuate path 22 with motor operation.

The provision of modular x-ray generator head assemblies allows thedifferent heads to be tailored for different part and materialrequirements for taking x-ray diffraction measurements therefrom. It iscurrently envisioned that the x-ray heads can be provided in differentsizes and configurations such as shown in FIGS. 3-5 and FIG. 28 withthere being a large x-ray head 12 (FIG. 3), an intermediate size x-rayhead 32 (FIG. 4), and a microhead 34 (FIG. 5). Also, a speciallydedicated x-ray head 200 (FIG. 28) can be provided that allows for x-raydiffraction measurements to be taken from a very particular partgeometry, as discussed more fully hereinafter. Accordingly, the presentapparatus 10 allows a single base unit 14 to be employed with severaldifferent x-ray heads such as the illustrated set of heads 12, 32, 34and 200. In this example, the x-ray head 12 can be employed where higherpower requirements are required for generating x-rays to takemeasurements from a particular part material, whereas the smaller heads32 and 34 can be used where the power is not as critical and access todifficult part geometries is needed. In particular, with the microtube34, it can be maneuvered into confined spaces such as found inside onthe interior of tubular parts for taking x-ray measurements from theinterior surfaces thereof. Head assembly 200 is specially adapted fortaking measurements from small through bores that are of a relativelyshallow depth such as the illustrated bolt holes 202 found in aircraftrotor discs 204.

Beyond size, the modular heads can be tailored in several other respectsas well. For example, the wavelength generated for the x-rays can betailored to the material to be measured so as to better match thelattice structure thereof. To do this, the material for the target anode36 at the forward high voltage end in each of the tube heads can bevaried. Exemplary anode materials can include copper, cobalt, wolfram,silver, molybdenum, manganese, iron and titanium. The beam shape can betailored to the piece to be measured as by providing differentcollimators 20 on the various x-ray heads. For example, for those piecesthat have surfaces in long narrow crevices or holes that are desired tobe measured, the collimator 20 can be configured to generate a narrowerx-ray beam to avoid measurement errors.

In addition to the collimator, an x-ray detector assembly 37 is providedas carried by each of the x-ray heads including x-ray detectors orsensors 38 and 40 that are typically mounted on either side of thecollimator 20 via an arcuate x-ray mount 42. The x-ray heads can havethe position of these detectors 38 relative to the collimator 20 variedalong the mount 42 or on differently sized mounts 42 from one head tothe other so that they are matched with the x-ray wavelength generatedby the head and the response of the material for which the x-ray head isto be used for taking x-ray diffraction measurements from. The mount 42itself can be shifted to provide for different measurement techniques orto accommodate different diffraction angles such as in assembly head200, as will be discussed hereinafter. As is apparent, the provision ofmodular x-ray heads such as x-ray heads 12, 32, 34 and 200 enables muchgreater flexibility in tailoring the apparatus 10 to the particularneeds of the x-ray diffraction operation that is to take place withoutnecessitating several different x-ray diffraction units for thispurpose.

Another feature of the preferred modular x-ray head apparatus 10 is theuse of an electronic control system that includes a programmable module43 associated with each of the x-ray heads 12, 32, 34 and 200, acontroller 44 associated with the base unit 14, and an electrical link46 that can interconnect the module 42 to the controller 44 with aselected one of the heads detachably connected to the unit 14. As can beseen in FIG. 2, the electronic link 46 can include a cable 48 connectedto the module 43 and having a pin connector 50 at its free end which isadapted to be plugged into a socket connector 52 secured to the baseunit 14. In one aspect, data flow to the controller 44 is not enabledunless the head is properly connected to the base unit via the adapter24. To this end, electrical contacts 53 a and 53 b can be provideddisposed on the adapter portions 26 and 28, respectively to be inelectrical communication when the portions are properly mated together.In this manner, the contacts also form part of the electrical connection46 for the control system. If the installation is completed successfullywith the contacts 53 a and 53 b in electrical communication, when thepin connector 50 is plugged into the socket connector 52, the controller44 recognizes that proper installation has occurred and autoconfiguresthe system to allow the measurement operation to properly proceed forthe selected head, as depicted in the flow chart of FIG. 20.

The module 43 can include programmable memory so that it can bepreprogrammed with information relating to the particular x-ray headwith which it is carried. For example, the x-ray heads can bespecifically tailored to measure a specific type of material or materialcharacteristic as by generating an appropriate amount of x-ray flux andx-rays in the wavelength necessary for obtaining diffractionmeasurements from the part to be measured therewith. Thus, when x-rayhead installation is successful, the controller 44 will have informationor system configuration data transmitted thereto such as relating to theparticular x-ray head that is attached to the base unit 14 such as thesize of its collimator 20, the material type of its anode 36, as well asthe size of the x-ray tube head itself and its power rating. Forexample, with the three different sizes of x-ray heads 12, 32 and 34discussed herein, each can have different power ratings correlated totheir size. Accordingly, the large x-ray head 12 may have a diameter ofapproximately four inches and a power rating of 3000 watts, theintermediate x-ray head 32 may have a diameter of approximately 1½″ anda power rating of 300 watts, and the micro x-ray head 34 may have adiameter of approximately one and one quarter inches down toapproximately three-eighths of one inch and a power rating of 200 wattsor less. In addition, the power requirements for a particular size oftube head can be varied such as when there are heads of the same sizethat have different target anodes 36 from each other. In each instance,the control system will be provided the power rating of the particularmodular x-ray head that is connected to the base unit 14 via theelectrical connection 46 provided between the programmable module 42 andthe controller 44. Once such information is received, the controller 44regulates power supply to enable operation of the x-ray head inaccordance with the power rating thereof.

Other variables between the x-ray heads which can be transmitted as datainformation to the controller 44 include the focal distance of the x-rayhead and the details of the x-ray detector system 37 such as detectortype or number of detectors, detector width and resolution provided bythe detectors. Also, if the x-ray head employs a detector configurationthat is fixed, the module 42 associated therewith can be programmed toindicate the measurement technique to be employed by the control systemas dictated by the predetermined fixed detector configuration.

The small or micro tube x-ray head 34 disclosed herein can includealternative cooling systems provided therefor. Referring to FIG. 6, thetypical cooling system for known x-ray heads employs cooling lines 56and 58 that feed and remove cooling fluid, such as water or a glycolbased fluid, to the tubular housing 54 via a fluid manifold 60 mountedto the forward or free end 62 of the head as by cap member 63 connectedthereto. As shown with respect to microhead 34, the cooling lines 56 and58 extend upwardly and then are run back toward the unit 14 along thetop of the housing 54. Such a configuration effectively increases thesize or diameter of the tube housing 54 in terms of its ability to beadvanced into confined spaces such as found on the inside diameter oftubular parts. Accordingly, an alternative cooling system is alsodepicted for the microhead 34 wherein the cooling lines 56 and 58,rather than extending back along the exterior of the tubular housing 54,continue forwardly from the x-ray head 34 through cooling line ports 63a and 63 b formed in the housing cap 63. In this manner, the coolinglines 56 and 58 do not increase the effective diameter of the tubularhousing 54 allowing it to be advanced into the interior of tubular partsthat may have only a slightly larger inner diameter than the diameter ofthe microtube housing 54 without encountering interference from thecooling lines 56 and 58 such as when they are run along the outersurface thereof.

Another adaptation for the microtube 34 in particular resides in the useof a flexible circuit board 64 including a circuit 66 printed thereonthat processes signals received from the detectors 38 and 40 on eitherside of the collimator 20. In prior x-ray heads, the detectors includecabling that extend therefrom generally upwardly to a control unit forprocessing x-ray signals which restricts the maneuverability of theseheads and their ability to access confined spaces. On the other hand,with the flexible printed circuit board 64 herein, only a very shortlength of fiberoptic cable 68 extending between the detectors 38 and 40and the circuit board 64 need be provided as the board 64 can be securedto the outer surface of the tubular housing 54 toward the end 62 thereofin close proximity to the detectors 38 and 40 and in substantialconformance therewith wrapped about the housing 54. In this manner, theeffective diameter of the tubular housing 54 is only nominally increasedas by the thickness of the thin printed circuit board 64 with theattendant advantage of removing the impediments caused by having largeand long lengths of cabling extending up from the detectors 38 and 40 toa fixed processing unit above the x-ray head as in prior systems.Accordingly, with the present flexible circuit board 64 includingcircuit 66 adapted for processing the x-ray detector signals, the lengthof the detector cables is minimized as it extends only for the distancebetween the detectors 38 and 40 mounted to the integrated arc mount 41at either end thereof to the outer surface of the tubular housing 54 towhich the circuit board 64 is secured. As can be seen in FIG. 6, thecircuit board 64 is formed of material that is of sufficient flexibilityto allow it to be bent and curved around the outer curved surface of thehousing 54 so that it is in flush engagement therewith when securedthereto.

As shown in FIG. 9, the micro tube head 34 includes a bottom recess 69toward the forward end 62 and having a window 70 aligned with thecollimator 20 which allows the passage of x-rays as generated in thetube 34 a and directed therethrough via the target anode 36 but keeps avacuum intact in the housing 54. Generally, these windows are brazed tothe material of the tubular housing via an intermediate brazingmaterial. However, the small volume inside the microtube housing 54along with the high vacuum required therein creates problems with theuse of brazing material such as due to melting thereof which cancontaminate the interior of the housing 54 as well as allow forundesired x-ray flux leakage therefrom. Accordingly, the preferredmicrotube housing 54 employs a window such as of a beryllium materialjoined to the stainless steel material of the tubular housing 54 byelectron beam welding so that an intermediate brazing material is notused. In this regard, the present miniature x-ray tube head 34 includingthe electron beam welded window 70 does not have brazing materialpresent and thus avoids the contamination and leakage problems foundwith brazed windows as is used in prior x-ray heads.

Referring next to FIGS. 28 and 29, the illustrated head assembly 200shown is especially well suited for taking x-ray diffractionmeasurements from the interior surfaces of throughbores such as theillustrated fastener through bore 202 in aircraft disc 204. The x-raytube 200 a can be oriented in a different configuration from thepreviously described tubes 12 a, 32 a, and 34 a via a carrier support206 therefor. In this regard, the x-ray tube 200 a can extend laterallyin the y direction transverse and, more specifically, perpendicular tothe orientation of the previously described x-ray tubes 12 a, 32 a and34 a.

The carrier support 206 can have a generally U-shaped configurationopening downwardly toward the part 204 from which x-ray diffractionmeasurements are to be taken with the x-ray tube 200 a provided with anoverhead support generally above and off to one side of the part. Morespecifically, the support 206 includes a rear, vertically extendingportion 208 which includes the socket adapter portion 28 toward thebottom thereof. Toward the upper end of the vertical portion 208, thereis a forwardly extending portion 210 including a hanger 212 thatsupports the x-ray tube 200 a forwardly of the rear support portion 200a and below the upper portion 210.

Frame portions 208 and 210 and hanger 212 include an adjustable mountingtherebetween as by adjustment slots 214 and associated guide fastenersthat allow the tube head 200 a to be vertically adjusted in the z-axisdirection and adjusted in the fore and aft x-axis direction. Inaddition, head assembly 207 includes an upwardly extending flange 218that has followers 220 for being adjustably secured in an arcuate guideslot 222 of the hanger 212 to provide for arcuate adjustments of thehead 207 in a compound x and z axis angular direction. By way of theadjustability provided by the carrier support 206, the position of thecollimator 20 can be adjusted to allow for the angle of attack of thex-ray beam emitted therefrom to be varied relative to the part 204, andspecifically the throughbore 202 having its axis 202 a extending in thex-axis direction. In this manner, the optimum orientation of the tube200 a and collimator 20 thereof can be achieved relative to theconfiguration and size of the through bore 202.

Similarly, the detector assembly 37 can be adjustably supported by thecarrier support 206, and specifically via a forward, downward extension224 thereof. As shown, the extension 224 projects downwardly from thefront end of the upper support portion 210 with the detector assembly 37including the arc mount 42 thereof being adjustably secured to slottedslide bracketing 226 to position the detectors on the side of the part204 opposite to the side at which the tube 200 a and collimator 20 aredisposed. The slide bracketing 226 can allow for x, y and z adjustmentsof the detector assembly 37, as can be seen in FIGS. 28 and 29. In thismanner, the detectors 38 and 40 secured to the arc mount 42 can havetheir position optimized for detecting x-rays defracted from the innersurface of the throughbore 202. In addition, the slide bracketing 226can allow for the mount to be angularly adjusted in path 228, as shownin FIG. 28.

As previously mentioned, the drive assembly 18 for oscillating the x-rayheads in their arcuate path 22 during an x-ray diffraction measurementoperation is integrated into the base unit 14 rather than beingintegrated with the x-ray head assembly and cantilevered forwardly alongwith the heads from the base unit 14 as in prior x-ray diffractionsystems. In this manner, the weight of the drive 18 does not affect thex-ray diffraction measurement operation either in terms of its speed orits accuracy unlike prior systems. As shown, the present x-ray headdrive assembly 18 includes a motor 72 that is mounted to the base unit14 as by bracket 74. The motor 72 includes a drive shaft 76 whichtransmits rotary power to the output shaft assembly 77 including endadaptor portion 26 thereof. In the illustrated and preferred form, thedrive assembly 18 includes worm gear transmission drive 78, as shownbest in FIG. 12. The drive shaft 76 extends transverse and inparticular, perpendicular to the output shaft assembly 77, and the wormgear drive 78 includes driver gear 80 on the drive shaft 76 and drivengear 82 on the output shaft assembly 77. In the preferred worm geardrive 78 herein, the driver gear may be a worm driver gear 80, and thedriven gear may be a worm wheel 82 with each of these gears 80 and 82including respective helical gear teeth 80 a and 82 a for being meshedin driving relation with each other.

To minimize measurement inaccuracies caused by backlash, theabove-described worm gearing 78 is provided with an anti-backlashmechanism 84, as can be seen in FIGS. 10-19. More particularly, the wormwheel 82 is split axially so that there are two annular gear portions 86and 88 which are angularly or rotatably biased relative to each other asby at least one and preferably two springs 90 and 92 such that the gearteeth 82 a stay in positive contact with the gear teeth 80 a atsubstantially all times even when the motor 72 reverses, such as whenthe x-ray head reaches an end of its arcuate path 22 during ameasurement operation. As shown in FIG. 14, the gear portion 86 is keyedto main shaft portion 94 of the output shaft assembly 77 so as to befixed up for rotation therewith as by a key slot 96 formed on theinterior diameter of the gear portion 86 and an axial projection 98formed on the main shaft portion 94 of shaft assembly 77. The gearportion 86 includes arcuate guide slots 100 and 102 (FIG. 15) extendingthrough the annular body 104 thereof. A pair of stand-off bosses orposts 106 and 108 extend axially from surface 104 a of the gear body104. The guide slots 100 and 102 are formed at diametrically oppositepositions in the gear body 104 so as to be spaced by approximately 180degrees from each other. The posts 106 and 108 are also diametricallyoppositely positioned to each other spaced by 180 degrees around thegear body 104 and by approximately 90 degrees from each of the slotopenings 100 and 102.

The gear portion 88 is mounted to the shaft portion 94 so as to freelyrotate with respect thereto. As shown in FIGS. 14 and 16, the gearportion 86 includes a hub portion 110 that extends axially from surface104 b, and which includes the slot recess 96 formed therein. The gearportion 88 also includes a pair of stand-off bosses or posts 112 and 114at diametrically opposite positions in the gear body 116 and whichextend axially from surface 116 a thereof. The gear body 116 alsoincludes a hub portion 118 which extends axially from opposite surface116 b of the gear body 116, as can be seen in FIG. 18. As shown in FIG.14, the inner diameter of the hub portion 118 is sized to beapproximately the same or slightly larger than the outer diameter of thehub portion 110 so that when the gear portions 86 and 88 are assembled,the hub 118 can rotate about the hub 110. Assembled, the biased gearportions 86 and 88 together cooperate to form the anti-backlashmechanism 84 for the drive assembly 18. For assembly of theanti-backlash mechanism 84, the gear portions 86 and 88 are advancedaxially relative to each other so that the respective gear body surfaces104 b and 116 a are brought into engagement with the posts 112 and 114aligned for fitting through the guide slots 100 and 102 and the hub 118sliding over the hub 110. With the posts 112 and 114 projecting throughthe slot openings 100 and 102, the springs 90 and 92 are then attachedso that they each extend between one of the posts 106, 108 of the gearportion 86 and one of the posts 112, 114 of the gear portion 88, asshown in FIGS. 11 and 13.

Accordingly, the preferred and illustrated anti-backlash mechanism 84includes a worm wheel gear 82 that is split axially into two annulargear portions 86 and 88 that are angularly or rotatably preloaded orbiased relative to each other so as to maintain positive contact betweenthe gear teeth 82 a of the split-gear 82 and the gear teeth 80 a of thegear 80, as is shown schematically in FIG. 19. In other words, thebiased gear portions 86 and 88 allow the respective drive teeth 86 a and88 a formed thereon to stay in engagement with the drive surfaces of thegear teeth 80 a at substantially all times during operation of the motor72 thus avoiding measurement inaccuracies caused by play betweenintermeshing gear teeth such as found in the prior rack and pinion drivesystems that have been previously employed in open beam x-raydiffraction systems. The springs 90 and 92 provides a bias force to thegear teeth 86 a and 88 a of the split gear 82 disposed between adjacentteeth 80 a of the gear 80 so that there is angular displacementtherebetween which allows them to stay in constant driving engagementwith the gear teeth 80 a such that one of the gear tooth portions 86 a,88 a is engaged with one tooth 80 a during motor operation includingduring reversals thereof while the other cooperating gear tooth portion86 a, 88 a stays in engagement with the next adjacent gear tooth 80 adespite sizing of the individual gear tooth portions 86 a and 88 a toprovide clearance between adjacent gear teeth 80 a when meshedtherebetween.

Referring to FIG. 19, the bias force provided to the split gear 82causes gear tooth portion 86 a and specifically drive surface 200thereof to stay firmly engaged with the left gear tooth 80 a andspecifically its facing drive surface 202, and the other cooperatinggear tooth portion 88 a and specifically drive surface 204 thereof tostay firmly engaged with the right gear tooth 80 a and specifically itsfacing drive surface 206. The surface 208 of gear tooth portion 86 aopposite its drive surface 200 is spaced from drive surface 206 of rightgear tooth 80 a and similarly surface 210 of gear tooth portion 88 aopposite its drive surface 204 is spaced from drive surface 202 of leftgear tooth 80 a. However, the preloaded split-gear 82 is able to take upthis gap spacing with one gear tooth portion or the other betweenadjacent gear teeth of gear 80 to maintain constant driving contacttherewith, as described above. Thus, with the anti-backlash mechanism 84herein, the play that would normally be found between gear teeth istaken up by the biased gear teeth portions 86 a and 88 a. Accordingly,the preferred drive assembly 18 herein incorporated in the base 14 andprovided with the anti-backlash mechanism 84 allows for preciseinformation to be known regarding the position of the head and thecollimator 20 thereof relative to the part 16 being measured.

Referring to FIGS. 16 and 18, the gear teeth portions 86 a and 88 a canbe oppositely tapered or contoured in the axial direction so that whenassembled they cooperate to form a concave surface 120 for the compositegear teeth 82 a formed by the cooperating gear teeth portions 86 a and88 a. The concave profile for the gear surface 120 allows it to betterconform to the tooth profile of the worm gear 80. In this way, there isgreater contact surface between the teeth 80 a and 82 a of the meshedgears 80 and 82 to optimize the load carrying capacity of the worm geardrive 78.

The micro tube 34 can have its detectors 38 and 40 fixed either as shownin FIG. 6 on either side of tube axis 34 a or alternately so that theyare aligned along the tube axis 34 a to improve the maneuverability ofthe tube 34 in confined spaces, as seen in FIG. 21. Manifestly, theother x-ray heads 12 and 32 can also have two versions so that bothmeasurement techniques can be employed with a particular x-ray tube headsize. As mentioned, with the sensors 38 and 40 axially aligned, themeasurement technique that is employed i.e. d v. Sine² χ, reducesmeasurement accuracy.

Referring now to FIGS. 22-26, a detector adjuster or shift assembly 122is shown which allows a user to shift the fiberoptic detectors 38 and 40between either of the two positions corresponding to the measurementtechnique desired to be employed, i.e. d v. Sine² ψ or d v. Sine² χ. Thedetector adjustment assembly 122 provides significant flexibility byallowing for either measurement technique to be utilized depending onthe needs of the measurement operation to be undertaken without the needfor changing x-ray heads or utilizing a different x-ray diffraction unitas previously required. Thus, if accuracy is not as critical andaccessibility to difficult to access spaces is more important, thedetector adjustment assembly 122 can be employed to shift the detectors38 and 40 so that they are aligned along the tube axis 12 a, as shown inFIG. 25 with the d v. Sine² χ measurement technique employed. On theother hand, where accuracy is more important than maneuverability of thex-ray head, the detectors 38 and 40 can be shifted to their positionwhere they are spaced laterally on either side of tube axis, as shown inFIGS. 23 and 24 rotated substantially 90 degrees from the position ofFIG. 25 for implementing the d v. Sine² ψ measurement technique.

Accordingly, the detector adjust assembly 122 obviates the need toprovide a different x-ray head for each of the two measurementtechniques. Although the assembly could be implemented with themicrohead 34, it has been found that to obtain the maximum benefits ofthe reduced size of the head 34, it is preferred to provide two versionsthereof as shown in FIGS. 6 and 21 with the detector arc mount 41 fixedor integrally formed with the tube housing 54.

The detector adjustment assembly 122 can include a manual actuator suchas in the form of a pull ring assembly 124 that allows an operator tomanually adjust the position of the detector assembly 37. Morespecifically, the assembly 122 includes a shift member in the form of arotary disk 126 having the detector mount 42 fixed thereto. The rotarydisk 126 can be secured in a selected one of two different positionsrelative to disk mount member 128 thereabove with the two positionscorresponding to the two x-ray diffraction measurement techniquesdiscussed herein. To this end, the disk mount member 128 includes a pairof apertures 130 and 132 that are spaced 90 degrees from each other tocorrespond to the d v. Sine² ψ and d v. Sine² χ measurement techniques,respectively.

The rotary disk member 126 carries a plunger member 134 of the pull ringassembly 124. The plunger member 134 is spring loaded in through bore136 formed in the disk member 126. The through bore 136 can be alignedwith either one of the apertures 130 and 132 to fix the position of thedetector system 37 as desired. Referring to FIG. 26, the through bore136 has a radially extending lip wall portion 138 extending about thebottom opening thereto. The plunger member 134 has a radially enlargedcollar portion 140 having a diameter that is larger than that of theapertures 130 and 132 in the disk mount member 128. Extending upwardlyfrom the plunger collar portion 140 is an upper pin portion 142 of theplunger member 134 sized to fit into the apertures 130 and 132. Spring144 biases the pin portion 142 in an upward direction and into one ofthe apertures 130 and 132 when aligned therewith. The spring 144 caninclude coils extending about the plunger member 134 with the end coilsseated against the wall portion 138 and the collar portion 140. Theplunger member 134 extends downwardly out through the opening formed bythe wall portion 138 and has a pull ring 146 secured at the lower endthereof.

As shown in FIGS. 23, 24 and 27, the pin portion 142 is biased into theaperture 130 such that the detectors 38 and 40 are disposed on eitherside of the tube axis and the d v. Sine² ψ measurement technique isemployed for x-ray diffraction measurement operations. To switch theconfiguration of the detector system 37, an operator pulls downward onthe plunger member 134 via the pull ring 146 so that the pin portion 142is retracted out from the aperture 130 against the bias force providedby the spring 144 with the spring coils compressed between the wallportion 138 and plunger collar portion 140. The operator then rotatesthe disk member 126 in rotary direction 148 as indicated by the arrow inFIG. 27 until the plunger member 134 is aligned with the aperture 132.At this point, the operator releases the pull ring 146 and the biasforce provided by spring 144 urges the pin portion 142 into the aperture132 of the mount member 128 to fix the position of the detector systemin the d v. Sine² χ orientation with the detectors 38 and 40 alignedalong the tube axis of the x-ray head.

Turning to more of the details, each of the x-ray heads 12, 32 and 34are mounted to a carrier support 150 that extends rearwardly from thex-ray head housing to depending flange mount portion 152 at the rear endthereof. The rear flange mount portion 152 includes the socket adapterportion 28 which is configured identically for each head and carriersupport 150 thereof including for head 200 and its previously-describedcarrier support 206. Each carrier support 150 includes a forwardlyextending cantilevered support portion 154 which carries the heads 12,32 and 34 thereon such that their respective longitudinal axes 12 b, 32b and 34 b extend generally in the fore and aft x-axis direction offsetfrom the socket axis 28 a and spaced thereabove. In this manner,operation of the common drive assembly 18 causes the heads 12, 32 and 34and their collimators 20 to traverse or sweep through the arcuate path22 which is centered on the offset axis 28 a of the socket adapter 28 ofeach of the heads. Similarly, the socket axis 28 a will generally beoffset from the tube 200 a of head assembly 200 so that operation of thedrive assembly 18 causes its collimator 20 to traverse arcuate path 22.Together, the shaft adapter portion 26 and the socket adapter portion 28cooperate to align each head in the same predetermined position eachtime one is connected to the base unit 14. Accordingly, with the any ofthe heads 12, 32, 34, and 200 detachably connected to the base unit 14,the shaft adapter axis 26 a will be aligned with the socket axis 28 a toprovide consistent and repeatable positioning of the modular x-ray headsherein.

Continuing reference to FIGS. 3-5, the carrier support 150 for thesmaller heads 32 and 34 can be substantially identical in terms of theforward cantilevered portion 154 thereof, whereas the support 150 forthe large x-ray head 12 can be modified to provide the heavier head 12with more robust support. As illustrated in FIGS. 1-3, the forwardextension portion 154 can have a cradle configuration including arcuateside portions 156 and 158 that extend up from the bottom around eitherside of the rear portion of the large x-ray head 12 to provide acradling thereof with underneath and side support for the head 12.Further reinforcement can be provided by gussetting 160 provided betweenthe rear end portion of the carrier support 150 and the depending flangeportion 152, as best seen in FIG. 3. By contrast, the smaller size andlighter weight of the heads 32 and 34 substantially obviates the needfor the robust construction for the carrier supports 150 thereof. Asshown, the intermediate size head 32 is carried out on front end portion162 of the carrier portion 154. The extreme light weight of themicrohead 34 allows it to be secured in line with the carrier portion154 so that its rear end 164 is secured in substantial face-to-facerelation to the front end 166 of the carrier support 150, as shown inFIG. 5. The aligned mounting of the microhead 34 also improves itsmaneuverability as the forward support portion 154 is substantially thesame diameter as that of the microhead's tubular housing 54.

Referring next to FIGS. 2, 10 and 12, it can be seen that the worm geardrive 78 is housed in an annular casing 168. The casing 168 includesfront and rear wall portions 170 and 172 that are counterbored forreceipt of high precision bearings such as ball bearings 174 and 176,respectively, therein. The shaft assembly 77 is journalled for rotationby the bearings 174 and 176 with the conical adapter portion 26projecting forwardly from the front wall portion 170. Bushings 177 canalso be provided about the shaft assembly 77, and in particular the mainshaft portion 94 for provided bearing support thereto. Radially enlargedfront and rear flanges 178 and 180 cooperate to capture the shaftassembly 77 tightly against and for rotation with the respectivebearings 174 and 176. As shown in FIG. 12, the rear flange 180 can beformed on a rear cap member 182 that is bolted to the rear end of themain shaft 94 for output shaft assembly purposes. The motor casing 168can be secured to or integrally formed with a y-axis carrier 184 at therear thereof that is mounted as by a dovetail fit to a z-axis carrier186 which can slide vertically up and down along vertical stand 188 ofthe base unit frame 19.

While there have been illustrated and described particular embodimentsof the present invention, it will be appreciated that numerous changesand modifications will occur to those skilled in the art, and it isintended in the appended claims to cover all those changes andmodifications which fall within the true spirit and scope of the presentinvention.

1. A method for testing parts by x-ray diffraction, the methodcomprising: identifying testing criteria for an x-ray diffractiontesting operation on a part to be tested; selecting an x-ray head from aplurality of different x-ray heads based on the identified testingcriteria; releasably connecting the selected x-ray head to a commondrive assembly; and driving the releasably connected x-ray head by thecommon drive assembly in a predetermined path to emit x-rays from thedriven head at the part to be tested.
 2. The method of claim 1 whereinthe driving of the releasably connected head in a predetermined pathoccurs in an arcuate path to direct x-rays at a region on the part froma variety of different angles.
 3. The method of claim 1 whereinidentifying the testing criteria includes identifying at least one ofconfiguration of the part to be tested and material of the part to betested.
 4. The method of claim 1 wherein the different x-ray headsinclude differently sized x-ray heads.